Shallow Loamy Pinedale Plateau (SwLy PP)
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Herbivory (continuous or season-long, low to moderate stocking)
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Transition T1B
Soil-disturbance (e.g. hoof action, rodents, water erosion) and high intensity fire or chemical and mechanical treatment
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Transition T1C
Extreme soil-disturbance (e.g. oil and gas development, road construction, heavy use areas)
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Transition T2A
Soil-disturbance (e.g. hoof action, rodents, water erosion) or catastrophic wildfire or chemical and mechanical treatment
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Transition T2B
Extreme soil-disturbance (e.g. oil and gas development, road construction, heavy use areas)
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Transition T3A
Extreme soil-disturbance (e.g. oil and gas development, road construction, heavy use areas)
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Reference State consists of two plant communities: the Big Sagebrush/Bunchgrass Plant Community and the Bunchgrass/Big Sagebrush Plant Community. Each plant community differs in percent composition and foliar cover of bunchgrasses and Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) as the dominant shrub. Forbs are a minor component.
Two important processes occur in the reference state and result in plant community changes: 1) sagebrush-killing disturbances such as herbivory, drought, prolonged soil saturation, freeze-kill, snow mold, and to a lesser extent, fire; and 2) time without those disturbances, generally referred to as "natural succession."
Fire is thought to have been infrequent due to low fine fuel loads, but when it occurred it was small acreage and stand replacing (Innes 2019). Fire Return Intervals are difficult to estimate due to little direct evidence of fire from pre-settlement times, but what information does exist suggests over 200 years for low fuel sites in the Wyoming Basin (Innes 2019).
Characteristics and indicators
The shift between plant community phases is dependent upon sagebrush-killing disturbances, and without them sagebrush will increase even with proper grazing management. Improper grazing management may accelerate the rate of increase for the shrub component.
Management actions or treatments are not typically prescribed or used to mimic the natural disturbance regime due to fragile nature of the soils and lower productivity potential on this site. Treatments that do exist many times have goals for increased leader growth on shrubs for big game winter range. Prescribed fire is not used due to land uses, ownership patterns and lack of fine fuels (Clause and Randall, 2014).
Resilience management
This site has moderate to moderately high resilience due to its aridic ustic (ustic bordering on aridic) soil moisture regime and frigid bordering on cryic temperature regime (Chambers et.al. 2014). Precipitation is typically low, but more effective with cooler temperatures and present when needed during the critical growth period (May through June). The site can usually recover after disturbance but is susceptible to delays in recovery during extreme climatic events such as drought.
The site has moderately high resistance to invasion by annual grasses because of climate limitations (dry and cold). The site may be susceptible to invasion after extreme disturbance during warmer climatic periods or on southeast aspects and concave microtopography.
At the LRU scale, this site is less resilient than Sandy, Loamy, or Clayey sites, and it is less resistant to invasion by annual invasive grasses when on south-facing aspects. Lower resilience and resistance is caused by slope, aspect, rock fragments, and reduced infiltration, making this site more susceptible to dry and drought conditions and harder for new perennial plants to become established.
Submodel
Description
The Grazing Resistant State consists of two plant communities: the Big Sagebrush/Short-stature Grass Plant Community and the Short-stature Grass/Big Sagebrush Plant Community. There has been a shift in under-story herbaceous species dominance from mid-stature cool-season bunchgrasses to short-stature, shallow rooted bunchgrasses and rhizomatous grasses and grass-likes. Gap interspace and bare ground increase, while herbaceous foliar cover decrease.
Characteristics and indicators
There are fewer mid-size bunchgrasses and they are typically found under the shrub canopy where they are protected from herbivory. The shrub canopy interspaces are occupied by grazing tolerant grasses as well as patches of bare ground that are sometimes connected. Canopy gaps and bare ground increase, while herbaceous foliar cover decreases. Drier site conditions result in lower productivity and less herbaceous production potential. Decreased infiltration is caused by increased bare ground patch size and lack of litter that acts as mulch in retaining soil moisture and retarding runoff.
In many cases, the transition to the Grazing Resistant State may have occurred many decades ago during an era of higher stocking rates and continuous grazing during the growing season. However, continual grazing during the critical growth period (roughly May-June) at proper stocking rates will facilitate the transition to this state or maintain it as a stable state.
Resilience management
Site resilience is lower than the Reference State. Site hydrology has been modified due to moisture being utilized by shallower rooting species. Therefore, the site is drier earlier in the season, lower in diversity, and unable to recover as quickly after a disturbance such as drought. This state is more drought-prone, and therefore sees wider productivity swings during dry versus wet years.
Site resistance to invasion by annual grasses is similar to the reference state, although there are more niches for undesirable annual forbs such as desert alyssum or annual invasive grasses such as cheatgrass to become established during favorable (hot/dry) conditions on southeastern aspects and concave micro-topography.
Submodel
Description
The Disturbed State is a result of soil-disturbing activities outside of the normal disturbance regime expected for this site. Examples are high intensity hoof action, anthropogenic activity, rodent activity, or prolonged soil saturation, which includes occasional irrigation. It may also occur after brush management (sagebrush treatment) preceded or followed by grazing that include high-intensity grazing use without appropriate recovery periods.
Brush management treatment methods are typically chemical (including 2,4-D or tebuthiuron) due to soil limitations to mechanical treatment. However, mechanical treatments do occur when large rock fragments are not present on the soil surface. Herbivory (including browse and/or insects) can contribute to disturbances affecting this state. High intensity fire could be a factor in maintaining this plant community by stimulating sprouting shrubs (rabbitbrush) and killing sagebrush.
The Disturbed State consists of one plant community, the Rabbitbrush/Rhizomatous Grass Plant Community. Soil erosion is accelerated because of increased bare ground. This state is maintained by recurrent disturbance and by soil erosion.
Characteristics and indicators
There is a shift toward sprouting shrub and rhizomatous grass dominance. Both green and rubber rabbitbrush may be present. Annual weeds such as desert alyssum, flixweed, and lambsquarter, are often present in small amounts (less than five percent composition by dry weight). Invasive annual grasses such as cheatgrass may occur in small amounts on southern aspects.
Resilience management
Site resilience is lower than the Reference State or Grazing Resistant State. Site hydrology has been modified due to moisture being utilized by shallower rooting species. Therefore, the site is drier earlier in the season and unable to recover as quickly after a disturbance. However, existing sprouting shrub canopy and remnant perennial vegetation provide some amount of resiliency. Site resistance to invasion by annual grasses is lower due to niches in the understory for establishment as well as the added factor of disturbance. Episodic and limited moisture is more suited to annual life forms during drought.
Submodel
Description
The Disturbed State is a result of extreme soil-disturbing activities outside of the normal disturbance regime expected for this site. Primary examples include road construction, oil and gas exploration, as well as livestock and recreation heavy use areas.
Characteristics and indicators
Primary indicators of this state are extreme soil disturbance associate with anthropogenic activities. Depending on the time since disturbance, recent climatic events, and reclamation efforts, the plant community could be dominated by annual weeds or it could be reclaimed to a variety of introduced or native species.
Resilience management
Site resilience is lower than the Reference State, but potentially higher than the Grazing Resistant or Disturbed States. Site hydrology modifications exist, but may be temporary if proper reclamation occurs.
Site resistance to invasion by annual forbs is lower due to an increase in soil disturbance allowing niches in the understory for establishment. Common annuals to invade this site include kochia, Russian thistle, and halogeton. Cheatgrass may be present if introduced with seeding efforts, but does not dominate the site or influence site dynamics.
Submodel
Mechanism
Herbivory pressure in excess of normal Reference State conditions. A typical scenario is continuous spring or season-long grazing with low stocking intensity.
Constraints to recovery
Recovery is inhibited by continued herbivory pressure, reduced seedbank, and drought conditions. Annual grasses may occur in small amounts when on southeast aspects and concave microtopography.
Context dependence
This transition typically occur over a long period of time with no sudden event to trigger the transition.
Mechanism
Soil-disturbance outside of the normal disturbance regime expected for this site. Examples include high intensity fire, high intensity hoof action, anthropogenic activity (e.g. mechanical and/or chemical treatments), recreational activities, rodent activity, or prolonged soil saturation, which includes occasional irrigation.
Constraints to recovery
Recovery is inhibited by consecutive disturbances over a relatively short time period and prolonged drought conditions. There is a risk of annual invasion on southeastern aspects and concave micro-topography.
Context dependence
This transition typically occurs after multiple consecutive disturbances.
Mechanism
Extreme soil-disturbance from anthropogenic activity such as oil and gas development, road construction, and heavy use areas for livestock production or recreation.
Constraints to recovery
Recovery is inhibited by soil depth, herbivory pressure, and prolonged drought conditions.
Context dependence
Soils are fragile, and this pathway could occur from one severe disturbance or multiple consecutive disturbances (e.g. livestock or recreation heavy use areas) and/or extreme conditions such as hot temperatures, extreme drought, or high intensity grazing without adequate recovery periods.
Mechanism
Soil-disturbance outside of the normal disturbance regime expected for this site. Examples include catastrophic wildfire, high intensity hoof action, anthropogenic activity (e.g. mechanical and chemical treatments), recreational activity, rodent activity, or prolonged soil saturation, which includes occasional irrigation.
Constraints to recovery
Recovery is inhibited by consecutive disturbances over a relatively short time period, herbivory pressure, and drought conditions. There is a risk of annual grass invasion on southeastern aspects and concave micro-topography.
Context dependence
This transition typically occurs after multiple consecutive disturbances.
Mechanism
Extreme soil-disturbance from anthropogenic activity such as oil and gas development, road construction, and heavy use areas for livestock production or recreation.
Constraints to recovery
Recovery is inhibited by soil depth, herbivory pressure, and prolonged drought conditions.
Context dependence
This transition is typically sudden after a mechanical disturbance, but can also occur with multiple consecutive disturbances (e.g. livestock or recreation heavy use areas) and can be exacerbated by hot temperatures and/or extreme drought.
Mechanism
Extreme soil-disturbance from anthropogenic activity such as oil and gas development, road construction, and heavy use areas for livestock production or recreation.
Constraints to recovery
Recovery is inhibited by soil depth, herbivory pressure, and prolonged drought conditions.
Context dependence
This transition is typically sudden after a mechanical disturbance, but can also occur with multiple consecutive disturbances (e.g. livestock or recreation heavy use areas) and can be exacerbated by hot temperatures and extreme drought.
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.